Oral History Transcript — Dr. James Gunn
This transcript may not be quoted, reproduced or redistributed in whole or in part by any means except with the written permission of the American Institute of Physics.
This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
Please bear in mind that: 1) This material is a
transcript of the spoken word rather than a literary product; 2) An interview
must be read with the awareness that different people's memories about an event
will often differ, and that memories can change with time for many reasons
including subsequent experiences, interactions with others, and one's feelings
about an event. Disclaimer: This transcript was scanned from
a typescript, introducing occasional spelling errors. The original typescript
Access form | Project support | How to cite | Print this page
See the catalog record for this interview and search for other interviews in our collection
James Gunn; February 10, 1975
ABSTRACT: Early childhood, education 1938-1962; astronomy interest; graduate school at California Institute of Technology, impressions of professors; interest starts for cosmology. Social and political climate at Rice University; interests in quasi-stellar objects and astrophysics; distance relationship of quasi-stellar objects-galaxy associations. Importance of pulsars, pulsars as energy source. Non-professional life. Also prominently mentioned are: Halton Christian Arp, John Bahcall, Geoffrey R. Burbidge, Beverly Oke; Mount Wilson Observatory, and Princeton University.
Wright:This is an interview with Dr. James E. Gunn in the Robinson Lab on the campus of the California Institute of Technology on February 10, 1975 by Paul Wright on behalf of the Oral History Program at California State University of Fullerton.
Gunn, let's start out by having you tell us at length about your childhood and your initial interest in mathematics and astronomy.
Gunn:Let me think. I guess Iíve been interested in astronomy since I was really very young. My father was an exploration geophysicist with Gulf Oil. He traveled all around the country. He very much fostered my interests in such things. As soon as I was able to read, which was shortly before the first grade, when I was six or so, he started feeding me science books of one sort or another and my interest grew in astronomy and by the time I was in second or third grade I had read everything that was at a level I could read that existed in the library. It seemed I really had other interests that came and went. But astronomy was really my first love all through childhood. When I was ten or twelve, I guess, I first started getting interested in building telescopes and that kept up all the way through high school and undergraduate years.
I began undergraduate school at Rice in 1957 without a really very clear idea of what I was going to do. I went in as a physics major; I had just about decided astronomy was a hobby — it was really a first love — but I decided that understanding other things about the nature of the world, elementary particles and nuclei, was what I wanted to do. So I took a double major in physics and math at Rice.
I had applications in graduate schools in mathematics and graduate schools in physics and just a couple, just for the hell of it, graduate schools in astronomy. Finally, I decided at the very last minute that I really liked astronomy enough to do it as a career. I came here to graduate school. And I havenít regretted it a minute, of course. It has been fantastically exciting and great fun; all the way through.
I did an article in Sky and Telescope—it must have been 1960 or 1961— on a photographic telescope which I had built through the summer of my undergraduate years. I think it was through that project that I really got into a little bit of the techniques that the traditional astronomers used in terms of instrument making and more-or-less what the science was all about. I donít think one ever has a very good idea of what a science is all about until one goes to graduate school [laugh] and finds out how it's practiced. But I found out that I liked it a lot. I knew, already knew, that I liked astronomy a lot. But I liked the way astronomy was done a lot, too. I think that really made up my mind. I came here in 1961 and got my Ph.D. in 1965, and I sort of got started in this cosmology game then through my thesis.
One of the main reasons I wanted to come to Cal Tech was to work with Robertson. He was a theorist in the field here. He was killed in a car crash the summer before my first year at graduate school. So I never even got to meet the man. When I came there was really nobody here doing relativity theory on the faculty; Robertson had just died and they hadn't replaced him. There was nobody on the staff here interested in cosmology.
Sandage was over at the other place on the Carnegie staff. I talked with him some but it was not too terribly easy for students to get to know those people very well. It was sort of a fluke; they had a guy visiting from the Jet Propulsion Lab named Estabrook as lecturer who taught a relativity course, so I got to take relativity. I really like it a lot and wanted very much to do something in it. It sort of spurred my desire to do something in cosmology. I had been thinking up until that time that I would do something in stellar interiors and stellar evolution, which is still a field of very much interest to me. But an opportunity came just sort of out of the blue to do a rather funny kind of research project which involved looking at a piece of blank sky and measuring essentially how bumpy the light was from just a piece of sky where you couldnít see anything. The bumps are contributed by sources that are too faint to see individually, too faint and distant to see individually. Some people at Chicago had been trying to measure the outer parts of the galaxies at very faint levels and had run into this phenomenon. There seemed to be noise that they couldn't get rid of, that apparently came from the sky. An explanation that they gave, sort of off the top of their heads, it was probably due to very distant galaxies that they couldn't see individually that contributed to this kind of grainy background.
So it became then interesting to try to look at this problem theoretically and see whether (a) that was what they were seeing, and (b) if that was what they were seeing, could you learn anything from it about the universe? Because you were clearly seeing very great depths and you couldn't see individual objects, maybe there was some kind of signature that cosmology gave to the stuff. So I worked on that, fairly successfu1ly actually, and as in most things in cosmology, it raised more questions than it answered. There was not a clean cosmological test about what kind of universe we live in, big bang, steady state, or what, but it at least indicated the sort of questions you had to ask in order to solve this problem, and I followed up on that. Several of my students have worked on related problems in the same area. It was great fun. There have been lots of side roads, but that's a very quick thumbnail sketch of how I got where I am.
Wright:Just for the record, when were you born and where did you grow up?
Gunn:I was born in 1938, in a little town in east Texas called Livingston, in the east Texas oil fields. As I said, my dad was an exploratory geophysicist and we moved all around. He would stay in one place typically between six months and a year. A year was a long stay and we would pick up and move, and I lived all over the southern part of the United States — Mississippi, Alabama, Georgia, Arkansas, Louisiana, Texas, Oklahoma.
Then, when I was in the fifth grade, I guess, my dad died and we moved to a little town in south Texas called Beeville where my mother had relatives. I guess you could say I grew up there. I went to junior high and most of high school there. My mother remarried when I was in 8th grade. She married an army man, as if she hadn't had enough moving around [laugh]. We spent a while in east Texas, in a little town called New Boston. Then I went and came back to Beeville to finish high school. I never had lived in a city with more than 10,000 people I guess, until I finally went to Houston to undergraduate school.
Wright:Now what was your family's reaction to your interests in mathematics and astronomy?
Gunn:Well, as I mentioned earlier, my father was a scientist and he really fostered that tremendously. My mother, I don't think, gave any encouragement or discouragement to me. She certainly helped me along, but it was mostly my father's help that got me started.
Wright:During your high school and undergraduate work, for the record, what impressions did you have of your electives?
Gunn:I generally liked them and I was rather careful to take courses that I thought I would enjoy. I've always enjoyed languages and history. I've also had some interest in history of science for a long time, although I have never taken a course in it. Undergraduate school was something of a transforming experience for me because the whole idea of culture [laugh], it kind of hit me when I was there. My father was a very cultured individual and there were always books and things around, but I never talked to people that were at all intellectual. So it was a real revelation. I was really discovering the world for the first time and I enjoyed it very much.
Wright:Did you ever take any courses in astronomy?
Gunn:Not as an undergraduate. They were not even offered at Rice, but I read very widely through public school days, and in undergraduate school I read a lot. So I think I had the equivalent of an undergraduate astronomy preparation by the time I went to graduate school. Plus a lot of practical experience I had building instruments.
Wright:Could you say something about these telescopes that you built?
Gunn:There were a long series of them. I guess I started out with small refractors that you could build from cheap lenses around. The first reflecting telescope I built was a four inch which I built as a freshman, no, eighth grade I guess, yes. It wasn't until after we had moved back to Texas as a sophomore in high school, I guess, that I seriously began thinking about building a big one. And I had never done any optical work up until that time. I had just used components that had been bought, mirrors and things, and I had done all the mechanical work myself.
I decided I would build an eight inch and I couldn't even think about affording a finished eight inch mirror. So I just thought Iíd have a try at doing it myself. And it was great fun. It took me about a year. But I did a reasonable job and got a real feel for things required of precision optical work [laugh]. Iíve never done any since, really. I finished that instrument in a form that could be used for visual observations, I guess, the summer after my senior year in high school. Then when I was an undergraduate, I got to thinking that the telescope was optically very good and I would go ahead and try to modernize it and make some sort of passable research instrument out of it. So I built an electronic drive which ran off storage batteries, so I could observe way out on a ranch several miles from town. I built a gadget which took twelve volts and converted it into 110 AC variable frequencies to drive the synchronous motor to drive the telescope and then all the guiding things to guide to make photographs and built the camera. Those were quite successful. The telescope still exists in my wife's mother's attic and I go and rob parts occasionally for a project when I need them [laugh].
Wright:Do you have any anecdotes you might care to offer about your work with this series of telescopes?
Gunn:I don't really know.
Wright:I know I recall Dr. Sandage talking about him interrupting the neighbors in the middle of the night when he was observing in his backyard in Iowa.
You were out some distance from the town?
The telescope was up on a sort of concrete pedestal. We had gotten permission from the people who owned the place to set up a semi-permanent mounting, we didn't have a building. So I would take the telescope out every time. Visitors occasionally came around. This one guy came around to check a nearby oil well. He was a little bit dismayed at what was going on. He didn't quite understand why we would be sitting out in the cold doing this kind of stuff [laugh]. But I don't remember anything terribly amusing that came out of this.
Wright:Now this doesn't relate to science, but what was the social, political atmosphere while you were at Rice?
Gunn:Well, it was in the days before students knew they should have, or felt they should have a voice in things. So it really was very quiet. There were little problems and things that came up.
Rice is organized on a residential college system; there are no sororities or fraternities. People are assigned to one of several residential colleges, but it does form the basis of their social life. The system really worked pretty well. I had friends — mostly friends in science, but not always — Rice had a fair number of philosophy and history major's. Rice was just beginning a transformation from a purely technical school to a university. In fact, while I was there they changed the name from the Rice Institute to Rice University. Then they began bringing in pretty good people from around. It was a very exciting sort of transitional time. Just at the end when I was leaving, students were beginning to feel their oats and deciding they should have a voice in things. That was sort of fun, too, though it had not reached the proportions that it did later.
Wright:Did your family support you financially in your education?
To a small extent. I was fortunate enough to win a set of Union Carbide scholarships which paid for most everything. Then while I was, there during my last three years, there were sort of achievement prizes which they gave to the top few students. And I was lucky enough to get one of those every year, so I was reasonably financially independent. Which was a good thing, I mean, my parents were certainly not poverty stricken but they were by no means wealthy.
Also at that time it was very nice because although Rice has since become a tuition supported institution, at that time it wasn't. It was in the charter of William Marshall Rice's will that education be free. Of course it was still expensive because of housing and board, books and stuff like that. They have since gone to a tuition system, although they have a very liberal scholarship policy, for tuition mostly.
Wright:During your graduate work at Cal Tech you were pursuing your work in astrophysics. Who were some of the professors here that impressed you?
Gunn:Most everyone who is here, actually, there has been rather little faculty turnover. I started working almost as soon as I got here and got into research with a guy named Bob Kraft, who is now at Lick, who was actually on the Carnegie staff at Santa, Barbara Street rather, than on the Cal Tech staff. That was partly because of a fluke; I had talked to him about things at Rice and he had a small research project to be done at Mt. Wilson, so I got into that right away. I was and have been very impressed by him.
The guy who I've worked with most closely here and one of the ones I worked with closely as a graduate student — although I didnít do my thesis with him — is Bev Oke, who is now Associate Director of the Observatories. Weíre both very much interested in instrumentation —pushing television technology, such things as that — trying to apply it to astronomy. We're doing quite a bit of that now.
I actually did my thesis with Guido Munch, and he's still here. He was a student of Chandrasekhar at Chicago and had gotten interested in a similar problem when he was a graduate student, the sort of graininess in the background light in the galaxy that is due to starlight scattered from dust in the plane. And he felt that perhaps some of the techniques he had used could be used on a cosmological problem. In fact, that was true, that's what got me started on the project. But as I got along working on the problem I had quite a bit of contact with Sandage, who, as you know, is an exceedingly interesting individual.
Physics, courses, a guy going through in astrophysics really takes as many physics courses as astronomy courses, I think. The fellow here that I remember — who everyone remembers once he had ever had him in a course — is Dick Feynman, who is just fantastic. I sat in and took several of his courses.
Wright:Would you care to relate any anecdotes about your lab work or some of these professors you mentioned?
Gunn:Iím not very good at anecdotes, I'm afraid. No, I really can't think of any off the top of my head.
Wright:I mean any strange things that happened in your lab work.
Gunn:No, not really. My graduate work was pretty uneventful insofar as things like that. Things really went pretty smoothly, or else I have repressed it [laugh]!
Wright:While you were working on your Ph.D., the discovery and the spectral determination and the unusual nature of the quasi-stellar objects was determined. How did your professors and some of your fellow students view them initially?
Well, it was a tremendously exciting thing based on the conventional interpretation that redshift was an indicator of great distance. Because they were so bright and so distant, the inference was that they were small and powerful sources.
I guess the attitude taken here has always been the one that has since gotten dubbed by various people as the conservative one. Though it was certainly true, that they had very strange properties, it was not evident in any real way that they violated any known law of physics. For want of a better explanation, it seemed best to use as a working hypothesis that the redshift really was cosmological; that they were at a great distances, and let us try to understand them that way. That was sort of the framework that my own research on the problem had taken here. It is obvious that there are people who obviously don't take that point of view, like Burbidge and Arp and a number of other people, I suppose, although I think they are the primary — at least the most vocal part — of the liberal radical faction or whatever you want to call it [laugh].
So I think there have been more propensities here to try to use them as tools of various sorts than to try and really push their bizarreness which I think lots of people have done. It is certainly true that we donít understand them. I think no one would [laughter interrupted] claim anything to the contrary, and they have been rather disappointing as tools — as cosmological tools.
Of course, the primary excitement was that since you could see these very large redshifts, if they are cosmological, you were probing the universe at very, very great distances and very, very early times. But they seemed to be so haphazard in their properties that itís very difficult to learn very much about the universe from them. They are by no means standard candles — even a single one is not a standard candle because they flicker so badly and as a class they are by no means standard objects.
I still have some hope that eventually there will be some sort of key to understanding from looking at the spectrum of a quasar to say how bright it really is. But that has eluded people to date and it really looks like they just come in all sort of sizes and types. I still don't think it's at all clear that they violate anything sacred that we understand in physics, but there are difficulties, to be sure.
Wright:How did you view astrophysics before you decided to make contributions in the field?
Gunn:Oh, poorly, I think. This bears on a comment I made earlier. I don't think that astronomy is any different from any other science. From this point of view, a student, an undergraduate student, really just does not know what research is all about. You learn it; it slowly sort of infuses into you through your graduate years as you begin doing it. But you really don't have very much conception. I had a fair conception about the kind of thing astronomers did, that you don't go and work at the telescope 365 nights a year, but you go and work a little while, then youíre faced with this stack of photographic plates or chart recordings or numbers of whatever that you sit down and have to figure out. I was aware of at least that which many graduate students are not even at that level. But that's a far cry from knowing what the flavor of research is and I think I had very little idea. I think most people going into science don't until they really have a go at it — you like it or you don't and I happen to thrive on it.
Wright:Your initial astronomical paper dealt with F type stars in the NGC 752. How did you come to write this paper?
Gunn:Well, this was a paper co-authored with Bob Kraft, who I told you about. Kraft was the guy that I told you I worked with when I first came here. And it was, actually on a problem related to this project that he had gotten me started with at Mt. Wilson. And the paper was an outgrowth of that. It was written when I was a second year graduate student, I guess. That was a project I started and finished and never really got interested in again: A question of temperatures, gravities and of main sequence stars and their spectra. A very interesting thing, I think we made some fair contribution to the field. It was kind of a one shot.
Wright:Your interests by 1965 had shifted to quasi-stellar objects and their impact on various cosmological models. How and why did your interests divert into this area?
Gunn:Well, I don't know. I was interested in cosmology and the quasars were there and they seemed to be interesting probes. You are referring to the paper by Peterson and Faulkner and me.
This was about the time that the Arp business was coming out in which people were beginning to say that they might be local. One of the hypotheses was that their redshifts might be just Doppler shifts with very high velocities and that these things had been ejected somehow from galaxies. They were nearby and had been ejected at great speeds and we saw them mostly red shifted. We see them redshirted when they go away from us, of course, but also, if they go at high enough speeds transversely, you get the transverse Doppler shift. So, in fact, this was one of the explanations, advanced, and what Peterson, and Faulkner and I did was to look at that carefully and show that it couldn't possibly work. That even though mostly you saw red shifted objects, the blue shifted ones are so much brighter because you get this sort of relativistic headlight effect, that you'd be able to see to an enormously greater distance and for any reasonable model you expect to see many, many more blue shifts than redshifts. I think that more or less killed that hypothesis. The other hypotheses, gravitational redshifts and various other things had been sort of dropping by the way. So the local people were left with some entirely mysterious mechanism for producing the redshifts.
Wright:That does remain one of the strongest arguments against non-cosmological interpretation.
Gunn:Well, it's a very strong argument against that particular non-cosmological interpretation. The controversy can be viewed in many lights. It's rather difficult to do anything decisive because the proponents of the local hypothesis are now sort of out of theories about what causes the redshifts and they're willing to wave their arms and say that nature does it some way — after all, these things break the laws of physics and we don't understand, and it's very difficult to say that can't be the case.
So, I've been working on this and a fair number of my publications deal with it one way or another. One of the things that occurred to me and co-workers early on was that we believe the redshifts of galaxies are cosmological and correct indicators of distance. And if we could find quasi-stellar sources that were in clusters of galaxies with the same redshifts, then that would be interesting and tend to indicate that they were cosmological. That is a current project, but it's a very slow thing. These things are very faint and I sandwich it in among other kinds of research projects. But that's been going on for a long time. There are five or six cases that we found in which the redshifts agree. And that's been done in what I think is a rather careful statistical fashion, so we can keep track just what these probabilities are at this, stage of the game, with these well determined samples, which is very important.
I think the problem with Arp's cases in which he has the connections between things that have greatly different redshifts, is that the sort of sampling is not well controlled. He is the first to admit this, and I don't really know what you do about it. You look at plates of zillions of things and there are some that are very strange — you look at those very hard and you find these connections. In order to assess them you have to know whether it's a chance super-position on the sky. And you can't really assess that chance unless you know exactly how the sampling was done. How many normal things were looked at before this one funny one turned up? You have to know the probability of finding that just by chance. And the way he does it, you just can't determine this probability, because he takes very deep photographs of these things and there are no corresponding photographs of control objects — normal objects — to compare with. Some of his examples are very disquieting, but it's hard to say what they mean. I think it's now become more a question of religion than science [laugh], which side of this fence you sit on.
Wright:Your paper on the accuracy of angular measurement in observational cosmology was intended, I would assume, to try and prove the data that is being taken. How did you come to write this paper?
Gunn:Well, as I said, from my thesis I was interested in this business of the bumpiness and the light in the night sky. So in the course of that investigation I looked at lots of effects which people really hadnít looked at before. One of them was the fact that if there is matter in space, then General Relativity says that gravitational fields bend light, so as light comes to us from very long distances, from very large distances it gets sort of wiggled about by the bumps of matter along the way, galaxies, and clusters of galaxies. One of the things that it does is introduce errors, real errors in how big you measure things to be and how bright you measure things to be. The bundles of light that come, get squeezed in shape and changed in size and changed in areas. So that paper and one which followed, which was something about the propagation of light in homogenous cosmologies — same sort of thing — looked into several of the different aspects of the problem.
Iím not really sure anymore that that's a terribly interesting problem because Iíve come around very strongly to the view from other sources, that the amount of matter in the universe is really very small and so these effects, even though they exist are probably not very big or very interesting. But that is definitely yet to be seen for sure.
Wright:In your paper on the propagation of light in homogeneous cosmologies, you tackled the problem of how light from QSOs and other high redshift objects might be affected. I think you probably already answered this question, but why did you choose to theorize on this subject?
Gunn:The same reason that was an outgrowth of the thing on angular diameters. It seemed an interesting problem that was sort of ripe for doing. Lots of things come up this way. It is hard to say why you do a specific problem. It's a problem which looks interesting but sort of occurs out of the blue, you know, and think, well, I can solve this problem. So you do it [laugh]. I think most of us, who are at all interested in observation or have programs that are ongoing and these are sometimes quite long things, I mean they go on for five years, ten years, and twenty years sometimes. But other little problems come along that may or may not be in that main stream, little side roads, we take them, just keeps life interesting.
Wright:It keeps you off the streets, says Dr. Sandage. [laugh] By 1969 your interests had been drawn to pulsars. How did you come to work with Ostriker on these objects?
Gunn:That was mostly due to Ostriker. I was at Jet Propulsion Lab for two years after I got my degree. Was actually in the Army, but was at Jet Propulsion Lab during that time. I had taken ROTC as an undergraduate, and I got a deferment to get my Ph.D. But, as soon as I got my degree, I had to serve my appointed time. That was just before Vietnam and the Army and NASA still had arrangements so that technical people could be shunted off into other technical activities. I was lucky enough to get landed at Jet Propulsion Lab for the time, for which I am eternally grateful.
But after that I had wanted to get into the academic world anyway and a position opened at Princeton, and so I went. Jerry had been working on the pulsar problem a little bit before and I got interested in it through him. We worked, I guess most of the time I was there, on one, or another aspect of pulsars.
Wright:The pulsars had been recently discovered?
Gunn:That's right. I went there in the fall of 1968 and they had been discovered only a few months before. It was a red hot thing to work on.
Wright:How do you perceive the importance of discovery of pulsars and the importance they've had to astronomy in general, cosmology in particular?
Gunn:Well, I don't think they've had very much cosmological impact. They were important for general astronomy from several points of view. They finally brought to everyoneís consciousness that neutron stars really existed and that they were an end point of stellar evolution. They were seriously talked about for a long time, since 1938, I guess — no, earlier than that — in 1932 or 1933, I think, Zwicky and Baade did the first paper.
Here they were, finally, I think everyone agreed that they were rotating neutron stars. They gave a lot better clues — now that they really existed it got people to thinking about them seriously — much better clues about what the super novae phenomena was all about.
They have proven to be very interesting probes of the interstellar medium, because as the radio waves come to us from them, the longer frequency waves travel more slowly than the high frequency ones because of dispersion due to ionized gas. The amount of that dispersion gives very accurate measures of the electron densities along the line of sight which couldn't have been gotten any other way. They have been part of this sort of whole revolution, that's been occurring in the theories in interstellar medium for the past several years; pulsars and the ability to do to some unique work from rockets and satellites, now especially the Copernicus satellite. We now have a very, very different picture of what the gas in the galaxy is like and conditions in it from the one we had in the pre-pulsar era.
I think also there was one very important thing they did, sort of an offshoot that they and the picture of them as rotating objects have finally brought home to astrophysicists the vast importance of rotation, to use it as energy storage. Essentially, astronomers discovered the fly wheel [Laugh] with pulsars and they had never quite thought about fly wheels before. Now, I think, it's very likely that the fly wheel phenomenon is important in lots of strange objects and I suspect perhaps in quasars as well, which may be nothing but giant pulsars. I donít really subscribe to that theory, but it could well be something like that.
Wright:Your model of the rotating neutron star and di-polar magnetic field decay is an acceptable theory for pulsars. Do you perceive this theory as being the most widely held theory among astrophysicists today?
Well, certainly that they're rotating magnetized neutron stars which are really Tommy Gold's idea, not ours. I think the notion that these very strong waves that Ostriker and I talked about from the rotating dipole — I think most people would agree that they play some part in the phenomenon. In a way, in the last few years, the data, if anything, has indicated that pulsars are a lot more complicated than anybody dreamed in the beginning. That is always the way it is, of course.
I think that anyone of the simple models including ours really canít hold in very much detail and there is something really a fair amount more complicated than in any of them that must be going on. I think itís still a very ripe field for working on. I think the foundations have been laid... more or less correctly.
Gunn:It's sort of at a point now where there is a vast amount of observational material which is virtually un-understandable on the basis of any of the simple models. I think there will be some sort of breakthrough. There are a lot of other people working hard.
Wright:You apparently became re-interested; I should say a continuing interest in quasi-stellar objects. How did you come to collaborate with Schmidt and Bahcall on the possible associations of QSOs with clusters of galaxies?
Gunn:Well, this occurred while I was still at Princeton. Bahcall was visiting there, and we had this idea of looking for clusters of galaxies around nearby — around low redshift-quasars, there. It had been thought of before, actually, but the two earliest ones whose redshifts had been measured to be 3C48 and 273 had been looked for rather carefully for clusters and none had been found. So it had sort of gotten into the lore that quasars were not associated with clusters. We decided that those two objects were very scant statistical data to base a statement so sweeping as that one.
We decided to look at the situation rather carefully and this involved taking deep plates of a sample of nearby ones, which we did. We discovered that, in fact there were very many which appeared to be at least on the sky — associated with clusters. And that's really how the whole thing got started. Then John came back here and told Maarten Schmidt about one of these objects. Maarten had a run coming up on the 200 inch with the spectrograph and he was in a position to get a redshift and he did and got the first one, B 234, which turned out to agree. And that sort of started the ball rolling, and there have been several since then.
Wright:That has been one that has continued.
Wright:A sort of continuing project. How did you come to work with Spinradís group at Berkeley and your fellow colleagues at Cal Tech on Maffei 1?
Gunn:That was sort of a circus. That work was done mostly at Spinrad's instigation. Actually, it was done mostly at the instigation of a student of Spinrad's.
The story goes — well, some background first. An Italian astronomer named Paolo Maffei, doing an infrared sky survey at one of the Italian Schmidtís, I don't know which one, and he was making a catalogue of infrared-bright objects. The two brightest things in his survey were Maffei 1 and 2. The story goes that this student of Spinradís read this paper — as he tells it anyway — while he was sitting on the ďjohnĒ one day. It came to him that these things might be nearby galaxies, perhaps very nearby galaxies that were being obscured by dust. So Spinrad got excited about it and told us down here about them, otherwise we probably would have never known they ever existed. Several of us got interested and it was sort of a task force. There were many people doing very, very different kinds of astronomy that all sort of ganged up. I forget how many, I think there were at least eight people. There were Oke, me and Sargent, and Neugebaur and Becklin from here, and Spinrad and Dieter and Landau, who was the student — I think there must have been at least nine, but I can't remember all the others.
So we all did our separate things and managed to put together a fairly coherent picture. The thing was, in fact, a rather nearby object, not as nearby as it might have been and hence not as interesting as it might have been, but really quite close to the Galaxy. I think we were able to paint a fairly convincing picture of what it was. We left open the question really of whether it belonged to the structure called the Local Group of which the Galaxy is a member. And I think that still isn't clear because the distance is uncertain by a factor of about two, the best we could do. If they are at the near end of that, they probably have to be included in the Local Group, but if they are further away, then they are probably not members. That is for someone else to work on.
Wright:You theorized that pulsars could be a source of energy for supernova remnants and visual supernovae. How do you perceive the acceptance of this theory at this time?
Gunn:I think it's widely ignored [laugh] perhaps with cause, I don't know. The supernova phenomenon has been the subject of a lot of inquiry lately. It is unfortunately influenced very much by really fundamental laws of physics and particularly the interaction of neutrinos with matter. So with all this stuff that has been happening about the; weak interaction and neutral currents, the subject has been very much in the state of flux. And I think really, until that settles down — we won't really know the relative importance of the various kinds of mechanisms that might make supernovae explode.
The pulsar mechanism is one which provides enough energy and does so on a reasonable timescale, but it's certainly in competition with more explosive things that might happen. I just don't think one knows yet and most of the attention is being put on those other things to try and understand them, and I think when it is all sorted out weíll know — maybe. Itís not entirely clear that we will know.
There's a very crucial question that's involved in that, which we donít know the answer to. That is that Ostriker's and my mechanisms for the supernova will only work if the pulsar' is born spinning very rapidly, so that there's a lot of energy stored in that fly wheel. We don't know in fact how rapidly neutron stars are rotating at birth and there are a lot of theoretical questions attendant to saying exactly what influences that rotation rate. If it turns out that somehow in the parent star that there is not enough angular momentum in the core to make it spin that rapidly when it collapses, I think, there's no question that it wonít work. But if there is, then that energy input is at least comparable to the more classical explosive ones. It has to be included in the overall scenario. But the whole situation is in a state of flux now, it's really impossible to say.
Wright:The true distance of the QSOs is of crucial importance on understanding the cosmological significance of these objects. How did you become interested in the distance of the PKS 2251+11 and other QSOs?
Gunn:Well, I mentioned that when Bahcall and I started working at this we had a sample of quasars that are relatively low redshift. In fact, we only looked at quasars with redshift less than 0.2. Classically, that means that they were receding at 20% of speed of light.
When I came here, I was still interested in the problem and realized that the sample should probably be extended because with the 200 inch at my disposal I could get considerably bigger redshifts for the galaxies that were in these clusters. So I more or less arbitrarily enlarged the redshift range to 0.36. As it turned out, I could have worked fainter even yet but I am stuck with that. There are now twenty-seven objects in the sample, all the quasars known at that time, with redshifts to 0.36. PKS 2251+11 was one of these objects. In the course of taking the photographs it became obvious that there was a very nice tight cluster around it and I made it one of my first priorities to try and get a redshift for one of the galaxies, and it turned out to be the same as the quasars.
That was an interesting case because it was the first such determination for a quasar which was real1y quite c1early a quasar by everyone's definition. That is, it was very much brighter — if you put it at a cosmological distance — than the brightest galaxy. It was a point like source that didn't have any fuzz around it, so it couldnít be ca11ed a Seyfert galaxy or an N galaxy. It was variable so it had most of the enigmatic properties that quasars had and it was clearly at the same distance as the galaxy. In fact, a much better redshift was determined somewhat later by Wampler using his machine which indicated that, in fact, the' redshift of the quasar in the galaxy agreed extremely well, better than my accuracy would allow. So that was gratifying. There are now several other cases of comparable kinds of objects, but that was the first.
Your interests apparently shifted somewhat to spectroscopy of galactic objects about this time. How did you become interested in the color changes, absorption variations of M31, M32 and NGC 4472?
Gunn:Well, you can't really say my interests shifted. That was just one of those little sidelines. I had, when I was at Jet Propulsion Lab, built a photoelectric spectrum scanner which was used on the twenty-four inch telescope that the Observatory had on the Table Mountain in the San Gabrielís. Spinrad had been at Jet Propulsion Lab and kept in contact with those people. So he knew about my instrument and it turned out that one of the nice things this instrument could do was to measure low, fairly low surface brightness things like galaxies away from the nucleus. So we hit upon this idea of looking at absorption lines, at how they change. This is sort of a tracer of chemical evolution. It was a fairly simple project to do. Spinrad had been interested in it before and he and McClure had started the whole business. But it was fairly clear that the chemistry of galaxies did change and it was an interesting kind of thing to look into. This machine was really suited to do it. So, we did it. Again, that was a sort of a one shot; I haven't really been interested in following it up.
Wright:The infall of material in the Coma cluster indicates the value of qo insufficient to close the universe. How conclusive do you consider this work and how do you perceive the importance of this work relative to the missing mass problem and galactic evolution?
Gunn:Well, I now think I have a whole host of better reasons than that for believing that qo is small. That one is very much in dispute and the reason is not so much that the analysis we did is wrong, but that we left out some effects which may be important. And the problem has been looked at again in very much more detail in a thesis that's very recently been done by a student named Susan Lee at Berkeley. She generally substantiates what we claim, but the analysis indicates that things we didn't consider, do go on. The analysis we made was quite simple and just was based on very simple ideas. We didn't do a full, scale computer study of what happened when gas falls in, that is what Susan tried to do. So I think that the conclusion still holds, although I personally regard it as a bit more dubious than I did, certainly when I first did it. It doesn't seem quite so iron clad as it did.
Since then, Richard Gott and I, here, we published a paper in collaboration with Schramm and Tinsley; now we have a whole host of other arguments which seem to indicate the same thing, that there is very, very much too little mass in the universe to close it. And that's based mostly on, in a way, similar kind of arguments, arguments about the dynamics of clusters of galaxies, the dynamics of the expansion locally, and things like this. And it's interesting that that conclusion goes along with the conclusion we reached in that infall paper. I no longer regard the infall result as terribly strong in itself because of these uncertainties.
That's a problem I intend to address again one of these days. There are lots of things on the back burner. I donít think Susan did the computer thing quite right. And it's not quite clear to me how, when you do it, in what I think is the right way, how things will change. Iím not sure whether it would be better or worse. But in any case, I think it needs to be looked at again for one or another of those things to be understood more thoroughly.
Wright:Your broad research interests were indicated when you collaborated with Jesse Greenstein and Jerome Kristian on a paper on the circular polarization of white dwarfs. Why did your interests shift into this area?
Gunn:Well, actually that's another one of those things that just sort of came along. You'll find quite a number of papers from people in this department that are like that. It wasn't a problem even that I was terribly interested in, but, there was this object that had just been discovered to have large circular polarization and perhaps that indicated that it had a very large magnetic field. I was interested in that aspect of it, because one of the puzzles has always been about neutron stars and pulsars. Those neutron stars do have a field 1012 gauss. But white dwarfs which are presumably come from stars just a little bit less massive than the stars that make neutron stars, typically have fields that are very small. And the question was, where do these enormous fields in neutron stars come from? And maybe we had been missing the magnetic fields in white dwarfs all this time and they really had what appeared to be a white dwarf with a very large magnetic field. So I was sort of interested in the object itself, and Jesse was actually the main instigator I think. Kristian and I both just mostly supplied observations. Jesse would say this was an interesting object, why don't you go and look at it on the mountain. So we looked at it. Jesse put everything together. As it turns out, the field wasn't really big enough to be very interesting from my point of view and I sort of lost interest in it at that point. [laugh]
Wright:Dr. Greenstein has had a long period of time and interest in white dwarfs.
Gunn:White dwarfs, that's right.
Wright:You've offered 323.1 as an example of a QSO in a rich cluster of galaxies with the same redshift as the cluster. Has a pattern or relationship been found between other QSOs and clusters of galaxies to permit more than a statement of probable relationship?
Gunn:Well, that's sort of left up to the reader. As I said in my sample, there are twenty-seven objects, and that includes all quasars with redshifts less than 0.36, that were known as of 1970. Out of those twenty-seven, there are now seven which both appear in the sky to be associated with clusters and have the clusters which have the same redshift as the quasar. The statistics are not terribly easy to do because it depends on how many big clusters of galaxies there are in space and that's something thatís only known to about a factor of two.
But the odds for a given one are like a part in a thousand, so the odds for seven of them to be there just by chance, are essentially zero.
I think one can say with some certainty that there are some quasars whose redshifts really give you their distance. These quasars are associated with clusters of galaxies. The simplest kind of scenario you can make is to say that quasars really are explosive events, in more or less ordinary galaxies — something funny happens in the nucleus that makes this thing, that makes them explode, either a black hole is formed or that some kind of a superstar formed, or something.
I wonít say that all quasars are cosmological—I would like to believe that — but what I have established is that some quasars are. So one is left with this funny dichotomy that maybe some are and some arenít, even though they look just alike, or else they all are and I will continue to believe the latter, but I donít, can't make the case until you put every single one in the cluster of galaxies and evidently some really don't belong in clusters of galaxies. But there are also galaxies that don't belong in clusters of galaxies. So maybe that's not too surprising. What I would like to do eventually is to show that — I need more cases — that quasars, cluster with other galaxies the same way that galaxies do with each other. That's a statistical problem. In other words, if you have a galaxy at random, it most probably is in a cluster. If you have a quasar at random, it most probably is in a cluster with the same probability. Now I think if I could demonstrate that, that those two things, those two statistical structures are the same, then that would indicate very strongly that quasars are events in galaxies and that they are in a cluster because the galaxy that the explosion is in is in a cluster. So that's sort of the eventual goal of all of this. But to do that conclusively really requires quite a number of cases and it is not quite clear whether it would be, even in principle, possible to do that with available data.
It's certainly true that you can say that within the errors, that's true now. But the errors are very big. And you need twenty or thirty cluster-quasar associations and there are not that many in the sample that I have got — there are only twenty or thirty quasars. But that's something for the somewhat far off future when I have looked a lot deeper and one can get redshifts a lot deeper.
Wright:From your method of detecting a cosmological density of cold, condensed objects, can you make comments on the implications for the missing mass problem?
Gunn:As you might have gathered, for some reason Iím very much interested in the missing mass problem and how to go about either finding it or ruling it out. This was a notion which was first investigated a long time ago, and it's a problem that's been floating around for a long time. It was Press, actually, who had the original, the initial idea, and, like a lot of past ideas, it turned out not to be original. But the object was, of course, addressed to this problem of how you find the missing mass, if it's there in some form in lumps. And it turns out that the techniques that you need to use are essentially the same ones that I've used before in the angular diameter paper and the inhomogeneous cosmology paper, just looking at the propagation of light through a medium that has lumps in it.
The conclusions we reached were that what the thing does if there are lumps is to make the images of distant objects double or triple or complicated if you look on at small enough scales. They are on the scales that people who do VLB, radio measurements see, scales of a thousandth of a second arc or so, for masses like globular cluster masses, bigger for bigger ones. Given enough data, you can say something about it. It began as one of those things that one doesnít have enough data in hand to say very much interesting. You can rule out the universe being closed by masses in a fairly interesting range of masses, from galaxy size on up. But we don't know that the universe can't be closed by baseballs or rocks or something of that size, or even things somewhat bigger. It's going to be a long time before one can say anything about that. There are arguments, however, which Gott and I came up with, that are in the Gunn, Schramm and Tinsley paper that do address this problem, that indicate really that matter cannot be in any of those forms either. There are several tests you can apply for missing mass of any form as long as it gravitates, and as far as we know, all mass gravitates. So it isn't there, at least not in the amount needed to close the universe.
Wright:Since you have worked so much with Ostriker, has your theoretical differences had any effect on your friendship?
Gunn:No. We do have theoretical differences. In particular the one about the missing mass. But the disagreements have been entirely good natured, I think. That isn't always true [laugh] in science, as you probably know.
Wright:Among your conclusions from the analysis study in distance determination of BL LAC., you found this object to have similar spectral properties as certain QSOs. However, the object has a relatively short distance from us and the relatively small redshift. What are your perceptions of the consequences of this work to cosmology and astronomy in general?
Well, I think it bears very strongly on the question of what and where the quasars are. BL LAC., is very bright, apparently very bright.
It was an interesting object for a long time because it showed no emission lines. However, it was clear that on photographs it was fuzzy, but it wasnít just a bright point like thing. There was a bright point like thing, and there was fuzz around it. Several people have suggested that fuzz might be a galaxy and BL LAC., was some kind of an event in the nucleus of the galaxy. So Oke and I decided that we would try to measure and find out if the spectrum of the fuzz was a galaxy. If it was a galaxy, presumably we could get the redshift if we could get the spectrum accurately enough. So we did. We built a special gadget for the spectrophotometer to do that, and we found that the spectrum was that of a more or less normal galaxy with a redshift of .07, which is small as quasar redshifts go, but BL LAC., is a lot brighter than most of the quasar's. So, at that distance the point like thing in the nucleus of BL LAC. is a very typical quasi-stellar source. It's some twenty times as bright as ordinary galaxies; at maximum it fluctuates wildly on time scales of days, months and weeks. Has a spectrum much like a quasar, essentially shares all the properties that quasars have except it does not have an emission line spectrum. I think it's fairly clear that the emission line phenomena have to be with material that's surrounding the quasar in any case. It doesn't really have to do with the nitty-gritty of energy generation, of this mysterious thing in the middle.
So we felt very happy about that, that this appeared to really substantiate that you could have an object which was very much more powerful than the galaxy, which did all these crazy things that quasar's did. In fact, it did it in spades, some things that even quasars don't do, but it did all those standard list of crazy things that quasars do.
The whole business of the variability and the enormous energy that is associated with the quasars if they are distant — those problems exist for BL LAC. as well. I think the main reason why the local people wanted to put them up close was that they get around these problems. But here is BL LAC., a galaxy whose redshift you can measure.
But Baldwin and Wampler and Margaret Burbidge have recently looked again at BL LAC. and they don't see spectral features. Oke and I had looked again at BL LAC. and had a new paper with Thuan and just submitted. We have looked very carefully again and find precisely the same results we found before. But this is clearly going to be a question that the air is going to be blue about for a while before anything is settled. [laugh]
Wright:The last paper you referred to, a paper dealing with BL LAC. What
does BL LAC. lack?
Gunn:That was a funny editorial that Geoff Burbidge wrote in Nature.
But there is a paper which I guess has just appeared in the Ap. J.
Letters, or will shortly, which describes the set of observations that the Lick people did on it. It's not really clear what the case is, I don't think they make a very strong case — but they presumably donít think Oke and I make a very strong case. [laugh] We will see Iím sure this is going to be resolved; it's just a question of finally getting data iron clad.
Wright:This is something that can be confirmed.
Gunn:Oh, yes, I think so. Itís not like the whole general quasar question which is a matter of philosophy, I think; this is a matter of fact!
Wright:In your recent paper on an unbound universe, you have determined that the high deuterium abundance after the Big Bang implies an open universe.
This is sort of my own idea, but is it possible to theorize from this that a small light fire ball might eject the universe with insufficient power to provide for a continuous expansion?
Gunn:No. The main disadvantage to this whole business of using the deuterium as a measure is that the theory is very simple and very naive. But there is really no indication that it isn't right. But, if you take the very simple theories of the Big Bang, the amount of deuterium that is produced is connected in a very intimate way with the density of matter in the universe.
The idea is simply that in the very early universe, the temperature is very high and it turns out that protons and neutrons exist in approximately equal quantities. Protons and neutrons can collide to make deuterium very easily. But that deuterium, in turn, can collide and make helium 3 and 4 very easily. So if the density is high, that means there are a lot of particles crowded into a small space and you make deuterium all right. But the deuterium is burned up almost immediately into heavier things, and so dense universes don't make very much deuterium because it all gets burned to helium. Actually, it stops at helium because there arenít any stable nuclear neuclei, at mass five weight, but, that is a technicality.
In low density universes, though, the proton-neutron collisions still go on to make deuterium; but the density is too low for very many of those deuterons to collide to make helium. Actually, a lot of helium does get made but the result is deuterium left over. So that if you see deuterium now, the argument is that density must have been low early and it turns out that you can predict from that what the density should be like now because we know what the radiation is now — we have the 3a blackbody radiation background now. In order to make enough deuterium now, the density had to have been sufficiently low at that time that now it corresponds to a very unbound universe by a factor of twenty or so.
You can't really argue about the strength or feebleness of the Big
Bang because it is all so tied up in the energetics of the radiation and the explosion and such. In fact the radiation was dominating the Whole show at that time. The universe is presumably matter dominated now, but if you go back far enough in the past, both the radiation and the matter are compressed, but the energy of the radiation increases faster when compressed.
So at that time the whole expansion, the whole dynamics was governed by radiation and by neutrinos and the matter was along for the ride, undergoing these trivial little nuclear reactions. The chemistry that got done during that time acts as a tracer of the conditions of the universe at a very early epoch.
I wouldn't think anything about it at all except that the helium production which is predicted is quite accurate. I mean, you measure helium in the universe today, and the theory says that the universe should have produced twenty-four to twenty-seven percent helium by mass and by God that's about how much helium there is. And that sort of makes you take seriously the whole picture of nucleo-synthesis in the Big Bang. So, if you believe it one step further and say if you're going to believe the helium you might as well believe the, deuterium, then the universe is unbound. So that's the tack we took. There are also other arguments in that paper, mostly dynamical arguments, about the behavior of clusters and groups which gives the same answer, and one can, in fact, put together a quite consistent picture of the universe from many, many arguments which all say there's a factor of twenty or so to little mass to bound the universe. There really isn't the enormous amount of missing mass which others think should be there. It is not missing, it is not there. [laugh]
Wright:Would you care to relate about any hobbies or ways you spent your leisure time?
Gunn:Oh, lots. I'm sort of a hi-fi freak. I got interested in electronics when I was in high school which has helped me tremendously in doing astrophysics. So I build, audio electronics and that takes up some of my time. Itís real1y funny; I grew up in Texas and never really discovered the out-of-doors. I did a little hunting and fishing with my companions, but I was never terribly enthusiastic about it. But in California I discovered mountains and I was immediately hooked. And so I hike a lot and climb a fair amount whenever I get a chance. The last three or four years Iíve taken, up skiing, too, and enjoy it very much. Whenever I get a chance, which isn't very often — I discovered it about the time I became too busy to do anything. [laugh] I try to get away. My wife and I collect graphics as well, and that is one of the main things we have in common — prints, lithographs, etchings, and such.
Wright:Are there any other aspects of your personal 1ife that you might care to relate?
Gunn:Deadly dull, I can't think of anything. I am rea1ly not very interesting. [laugh]
Wright:Well, youíre an awfully busy person.